refactor(tvix/store/pathinfosvc): use Arc<dyn …>

This removes the use of generics, like previously done with Blob and
Directory services.

Change-Id: I7cc8bd1439b026c88e80c11e38aafc63c74e5e84
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8751
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/store/src/tests/utils.rs

@@ -17,6 +17,6 @@ pub fn gen_directory_service() -> Arc<dyn DirectoryService> {
 pub fn gen_pathinfo_service(
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
-) -> impl PathInfoService {
-    MemoryPathInfoService::new(blob_service, directory_service)
+) -> Arc<dyn PathInfoService> {
+    Arc::new(MemoryPathInfoService::new(blob_service, directory_service))
 }